Cellular communications systems are well known in the art. In a cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells” which are served by respective base stations. Each base station may include one or more base station antennas that are configured to provide two-way radio frequency (“RF”) communications with fixed and mobile subscribers that are located within the cell served by the base station. Typically, a base station antenna includes at least one vertically-oriented linear array of radiating elements.
In many cases, each base station is divided into “sectors.” In a common configuration, a hexagonally shaped cell is divided into three 120° sectors, and each sector is served by one or more base station antennas. The linear array of radiating elements on each base station antenna may have a radiation pattern (also referred to herein as an “antenna beam”) that is directed outwardly in the general direction of the horizon, where the radiation pattern has an azimuth Half Power Beamwidth (HPBW) of approximately 65° so that the radiation pattern will provide coverage to the full 120° sector.
As demand for additional capacity has increased, the use of multi-band base station antennas has become widespread. A multi-band base station antenna includes multiple vertically-oriented linear arrays of radiating elements that are mounted on a common backplane. Typically somewhere between two and four linear arrays of radiating elements are provided, with one or more of the linear arrays providing service in a first frequency band and the remaining linear arrays providing service in one or more additional, different frequency bands. One common multi-band base station antenna design is the RVV antenna, which includes one linear array of “low-band” radiating elements that are used to provide service in some or all of, for example, the 694-960 MHz frequency band (which is often referred to as the “R-band”) and two linear arrays of “high-band” radiating elements that are used to provide service in some or all of, for example, the 1695-2690 MHz frequency band (which is often referred to as the “V-band”). The three linear arrays of radiating elements are mounted in side-by-side fashion. Another known multi-band base station antenna is the RRVV base station antenna, which has two linear arrays of low-band radiating elements and two (or four) linear arrays of high-band radiating elements. RRVV antennas are used in a variety of applications including 4×4 multi-input-multi-output (“MIMO”) applications or as multi-band antennas having two different low-bands (e.g., a 700 MHz low-band linear array and an 800 MHz low-band linear array) and two different high bands (e.g., an 1800 MHz high-band linear array and a 2100 MHz high-band linear array).
RRVV antennas and other antennas that include four or more linear arrays and/or two or more linear arrays of low-band radiating elements may be challenging to implement in a commercially acceptable manner because operators typically desire base station antennas that are relatively narrow in width, such as base station antennas with maximum widths in the 300-380 mm range. Mounting two low-band linear arrays and/or four or more total linear arrays side-by-side within this relatively narrow space while maintaining acceptable performance may be difficult.